Pristine Metal-organic Frameworks Research Articles

Design of Ligand-Nonbridging Sites in Metal-Organic Frameworks for Boosting Lithium Storage Capacity.

Metal-organic frameworks (MOFs) are lagging in the use of lithium-ion batteries (LIBs), ascribing to full coordination between metal nodes and organic ligands, to a large extent. By integrating a modulator into a ligand with missing bridging functionality, this study elucidates the role of non-bridging defect sites in MOFs in tailoring lithium storage performance. A fully bridged pristine MOF (p-MOF) utilizing the meso-tetra(4-carboxylphenyl) porphyrin ligand is compared with a modified MOF containing non-bridging defects (d-MOF) introduced by a homologous ligand, tris(4-carboxyphenyl) porphyrin. Spectroscopic and cryogenic low-dose electron microscopy techniques verify the presence of non-bridging defect sites in the d-MOF and reveal their explicit local structure. Density functional theory calculations show significantly enhanced Li+ adsorption energies and reduced Li+ migration barriers at the non-bridging sites in the d-MOF compared to the fully bridging sites in the p-MOF. As a result, the d-MOF exhibits exceptional lithium storage performance, achieving a high capacity of 761 mAh g-1 at 0.05 A g-1 and superior rate performance of 203 mAh g-1 at 5 A g-1, which substantially outperform the p-MOF. This study highlights the potential of modulating MOFs with non-bridging defects to develop high-performance LIBs.

Design of Ligand‐Nonbridging Sites in Metal‐Organic Frameworks for Boosting Lithium Storage Capacity

Metal‐organic frameworks (MOFs) are lagging in the use of lithium‐ion batteries (LIBs), ascribing to full coordination between metal nodes and organic ligands, to a large extent. By integrating a modulator into a ligand with missing bridging functionality, this study elucidates the role of non‐bridging defect sites in MOFs in tailoring lithium storage performance. A fully bridged pristine MOF (p‐MOF) utilizing the meso‐tetra(4‐carboxylphenyl) porphyrin ligand is compared with a modified MOF containing non‐bridging defects (d‐MOF) introduced by a homologous ligand, tris(4‐carboxyphenyl) porphyrin. Spectroscopic and cryogenic low‐dose electron microscopy techniques verify the presence of non‐bridging defect sites in the d‐MOF and reveal their explicit local structure. Density functional theory calculations show significantly enhanced Li+ adsorption energies and reduced Li+ migration barriers at the non‐bridging sites in the d‐MOF compared to the fully bridging sites in the p‐MOF. As a result, the d‐MOF exhibits exceptional lithium storage performance, achieving a high capacity of 761 mAh g−1 at 0.05 A g−1 and superior rate performance of 203 mAh g−1 at 5 A g−1, which substantially outperform the p‐MOF. This study highlights the potential of modulating MOFs with non‐bridging defects to develop high‐performance LIBs.

Ab Initio Molecular Dynamics Investigation of Water and Butanone Adsorption on UiO-66 with Defects.

Volatile organic compounds (VOCs) are harmful chemicals that are found in minute quantities in the atmosphere and are emitted from a variety of industrial and biological processes. They can be harmful to breathe or serve as biomarkers for disease detection. Therefore, capture and detection of VOCs is important. Here, we have examined if the Zr-based UiO-66 metal-organic framework (MOF) can be used to capture butanone─a well-known VOC. Toward that end, we have performed Born-Oppenheimer ab initio molecular dynamics (AIMD) at 300 and 500 K to probe the energetics and molecular interactions between butanone [CH3C(O)CH2CH3] and open-cage Zr-UiO-66. Such interactions were systematically interrogated using three MOF structures: defective MOF with a missing 1,4-benzene-dicarboxylate linker and two H2O; pristine MOF with two H2O; and pristine dry MOF. These structures were loaded with one and four molecules of butanone to examine the effect of concentration as well. One-molecule loading interacted favorably with the defective structure at 300 K, only. In comparison, interactions with four-molecule loading were energetically favorable for all conditions. Persistent hydrogen bonds between the O atom of butanone, H2O, and μ3-OH hydroxyl attachments at Zr nodes substantially contributed to the intermolecular interactions. At higher loadings, butanone also showed a pronounced tendency to diffuse into the adjoining cages of Zr-UiO-66. The effect of such movement on interaction energies was rationalized using simple statistical mechanics-based models of interacting and noninteracting gases. Broadly, we learn that the presence of prior moisture within the interstitial cages of Zr-UiO-66 significantly impacts the adsorption behavior of butanone.

Functional metal-organic frameworks derived electrode materials for electrochemical energy storage: a review.

Pristine metal-organic frameworks (MOFs) are built through self-assembly of electron rich organic linkers and electron deficient metal nodes via coordinate bond. Due to the unique properties of MOFs like highly tunable frameworks, huge specific surface areas, flexible chemical composition, flexible structures and a large volume of pores, they are being used to design the electrode materials for electrochemical energy storage devices. As per the literature, MOFs (including manganese, nickel, copper, and cobalt-based zeolitic imidazolate frameworks (ZIFs), University of Oslo (UiO) MOFs, Hong Kong University of Science and Technology (HKUST) MOFs and isoreticular MOFs (IRMOFs)) have attracted much attention in the field of supercapacitors (SCs)/batteries. According to their dimensionality such as 1D, 2D and 3D, pristine MOFs are mainly used as SC materials. Highly porous materials and their composites are capable for intercalation of metal ions (Na+/Li+). Moreover, the supramolecular features (π⋯π, C-H⋯π, hydrogen bond interactions) of redox stable MOFs provide better insight for electrochemical stability. So, this review provides an in-depth analysis of pure MOFs and MOF derived composites (MOF composites and MOF derived porous carbon) as electrode materials and also discusses their metal ion charge storage mechanism. Finally, we provide our perspectives on the current issues and future opportunities for supercapacitor materials.

Engineering a Cu-Pd Paddle-Wheel Metal-Organic Framework for Selective CO2 Electroreduction.

Optimizing the binding energy between the intermediate and the active site is a key factor for tuning catalytic product selectivity and activity in the electrochemical carbon dioxide reduction reaction. Copper active sites are known to reduce CO2 to hydrocarbons and oxygenates, but suffer from poor product selectivity due to the moderate binding energies of several of the reaction intermediates. Here, we report an ion exchange strategy to construct Cu-Pd paddle wheel dimers within Cu-based metal-organic frameworks (MOFs), [Cu3-xPdx(BTC)2] (BTC=benzentricarboxylate), without altering the overall MOF structural properties. Compared to the pristine Cu MOF ([Cu3(BTC)2], HKUST-1), the Cu-Pd MOF shifts CO2 electroreduction products from diverse chemical species to selective CO generation. In situ X-ray absorption fine structure analysis of the catalyst oxidation state and local geometry, combined with theoretical calculations, reveal that the incorporation of Pd within the Cu-Pd paddle wheel node structure of the MOF promotes adsorption of the key intermediate COOH* at the Cu site. This permits CO-selective catalytic mechanisms and thus advances our understanding of the interplay between structure and activity toward electrochemical CO2 reduction using molecular catalysts.

Defect strategies in Mn-doped metal–organic frameworks to enhance adsorption-based NOx gas sensing performance

Post-synthetic metalation (PSM) represents a powerful toolkit for modifying the chemical composition of pre-formed metal-organic frameworks (MOFs). However, accessing defective MOFs with exchanged metal nodes via this approach remains challenging. Herein, we report a transmetalation strategy to induce desired metal exchange frustrated flexibility defects in a prototypical MOF platform. Specifically, the pristine Zn-based MOF undergoes selective Zn-to-Mn exchange through a carefully controlled solvothermal transmetalation process. This protocol generates a series of Mn-doped MOFs with increasing Mn integration and the concomitant formation of defect sites within the framework. Detailed structural characterization confirms the successful Mn doping and illuminates the generation of vacancies and distortions around the exchanged Mn nodes. The transmetallated Mn-doped MOF materials exhibit altered chemical environments, as probed by spectroscopic techniques, and display promising sensing activity for NOx through the MOF matrix membrane. The proposed application of the MOF samples as an adsorbent-based chemical sensor includes sensing mechanisms for NO2 gas.

Reaction-assisted MOF manipulation for synthesis of UIO-66-NHCHO topology for prodrug fabrication: pH-responsive targeted drug delivery

A pH-responsive metal-organic framework (MOF)-based prodrug was synthesized via a premeditated formic acid-assisted amide reaction to form the UiO-66-NHCHO topology from UiO-66-NH2. This topology can be covalently attached to the methotrexate drug (MTX) to form theUiO-66-NH-HCN-MTX prodrug. The pristine MOF, UiO-66-NHCHO, and prodrug were characterized using PXRD, FT-IR, FE-SEM, BET, TGA, and NMR analyses. The solid-state NMR and FT-IR confirmed UiO-66-NHCHO topology.The loading efficiency and capacity of the prodrug were 88.96 % and 100.07 mg/g, respectively. These values were 12.90 % and 13.25 mg/g higher than those of the MTX-loaded MOF. This confirms the role of bonding in prodrug synthesis, beyond merely loading MTX through drug adsorption. At low pH the applied prodrug was activated due to CN cleavage. By decreasing pH from 7.4 to 5.5, imitating a tumor environment, the cumulative release of MTX increased by 64.94 %. This release rate was reached by 550 min, which was 230 min longer than the maximum MTX release from the loaded MOF. Such a premeditated delay can effectively suppress the burst release of MTX. At both pH levels, the Higuchi release kinetic model fit the release data better than other models, demonstrating that diffusion through the MOF pores controls drug delivery.

Thiol-functionalized conductive Co-MOF and its derivatives S-doped Co(OH)2 nanoflowers for high-performance supercapacitors

The low conductivity of many traditional metal–organic-framework (MOF)-based electrode limits their developments in the field of electrochemical energy storage and still of great challenge. The controllable preparation of various kinds of nanomaterials using thiol-functionalized MOF shows great prospects. In this work, a thiol-functionalized metal–organic framework sheet structure (Co-MOF/NF) on nickel foam was successfully prepared by in situ interfacial growth synthesis, which was transformed into its derivatives S-doped β-Co(OH)2 nanoflowers Co-x/NF (x = 1, 2 and 6) in different concentrations of KOH solutions through ion etching/exchange reaction. The pristine thiol-functionalized Co-MOF/NF and its derivatives Co-x/NF (x = 1, 2 and 6) nanoflower-like arrays could be used as positive electrode materials for effective supercapacitors. Among them, the transformation of the nanoflower-like Co-1/NF electrode exhibits excellent electrochemical properties with high areal capacitance (1925 ± 23 mF/cm2 at 1 mA/cm2), good rate performance, excellent conductivity and decent cycling stability. The Co-1//AC ASC device provides a high energy density of 0.176 mWh/cm2 (92.6 Wh/kg) at a power density of 0.745 mW/cm2 (392.1 W/kg). And this Co-1//AC ASC device exhibits a good cycling stability and practical application in energy storage field. This study provides a new strategy for the pristine thiol-functionalized MOF and its conversion nanostructures for energy storage applications.

Bifunctional PAni@Bi/Ce metal organic framework-Chitosan composite for electrochemical sensing and energy storage applications

Tailoring pristine metal-organic frameworks (MOFs) offered a great opportunity in exploring electrochemical sensing and energy storage applications. This study presents a novel Polyaniline@Bi/Ce MOF-Chitosan composite synthesized via a solvothermal method and chemical oxidative polymerization. PXRD, FTIR, SEM, EDAX, and TEM characterization confirmed its structural and morphological properties. Electrochemical performance was evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and electrochemical surface area (ECSA) analysis. The composite exhibited excellent electrocatalytic activity for detecting azithromycin and toluene with low detection limits and broad concentration ranges, demonstrated by voltammetry and amperometry. It showed significant stability for long term applications. Additionally, the material's energy storage capabilities were assessed through CV and galvanostatic charge-discharge (GCD) studies, revealing a specific capacitance of 415.32 F/g at 1.0 A g-1 and 90.48 % capacity retention after 5000 cycles at 6 A g-1. These findings highlight the Polyaniline@Bi/Ce MOF-Chitosan composite as a promising candidate for electrochemical sensing and energy storage applications.

Continuous flow synthesis of MOF UTSA-16(Zn), mixed-metal and magnetic composites for CO2 capture – toward scalable manufacture

UTSA-16(Zn) is a zinc and citrate-based metal-organic framework (MOF) which has shown highly promising performance for CO2 capture. However, the transition of this MOF to industrial application has been hindered as a scalable synthesis method has not yet been reported. Herein we report the first scalable continuous flow synthesis of UTSA-16(Zn), demonstrating a production rate of 173 g/h, which is a 77-fold increase compared to previously reported batch methods. Sustainability of the synthesis was maximised using low-cost non-toxic reagents and a low-energy flow reactor operating at atmospheric pressure. Chemical (reactant ratios, Zn/Mg mixed-metal) and process parameters (solvent ratio, flow rate, temperature) were optimised to continuously produce UTSA-16(Zn) which also demonstrated a high CO2 adsorption capacity up to 3.8 mmol/g and conversion yield of up to 66 %. Pristine MOFs are typically thermally insulating, thus thermal regeneration is challenging. To overcome this limitation, magnetic nanoparticles can be embedded within the MOF. This enables fast and energy efficient regeneration through magnetic induction heating. Here, citrate-coated Fe3O4 magnetic nanoparticles (MNP-CA) were successfully incorporated into the flow synthesis process of UTSA-16(Zn) to form UTSA-16(Zn)@MNP-CA magnetic framework composites (MFCs), representing the highest production rate reported of any MFC to date (152 g/h c.f. 13 g/h for MgFe2O4@UiO-66-NH2). UTSA-16(Zn)@MNP-CA MFCs demonstrate rapid heating under a magnetic field (26–150 °C in 60 s). The flow method developed herein is also widely applicable for scalable manufacture of other MOFs and MFCs, enabling their broader transition towards industrial applications.

Synthesis and investigation of charge storage characteristics in Ni-MOF/PANI composite as an active electrode material for supercapacitor

This study aimed to develop a more stable and efficient energy storage device, synthesis of nickel-based pristine metal organic framework (MOF) and combined it with the emeraldine base phase of polyaniline (PANI) which is confirmed with XRD, SEM and TEM. Both Ni-MOF and PANI exhibit faradaic (battery-like) behaviour. However, when these two materials are combined, the stability of the resulting material is enhanced. The initial materials, MOF and PANI, exhibit specific capacities of 42 C/g and 72 C/g, respectively. However, when these two materials are combined, their composite exhibits an enhanced specific capacity of 122 C/g. The cyclic voltammetry (CV) analysis shows oxidation and reduction peaks, indicating faradaic behaviour. This behaviour is further confirmed by electrochemical impedance spectroscopy (EIS). Upon comparing it with prior results, the specific capacity appears to be slightly lower. However, it is anticipated to exhibit stronger stability, which is contradictory. The composite material (Ni-MOF/PANI) exhibits remarkable capacitive retention of 99.25 % even after undergoing 5000 cycles, as anticipated. In order to validate the aforementioned findings and determine the extent of the current contribution from capacitive and diffusive control, Dunn's model was employed. The data demonstrates the prevalence of diffusive-controlled (faradaic) current over capacitive current. The highest proportion of current resulting from diffusion is 96 %, achieved at a scan rate of 5 mV/s. The highest proportion of current resulting from capacitance is 24 %, achieved at a scan rate of 300 mV/s. At lower scan rates, the material exhibits a greater faradaic behaviour, whereas at higher scan rates, there is a progressive increase in non-faradaic processes. The insufficient time for diffusive process at higher scan rates is the cause. The Dunn's model with quadratic correction is also performed and comparative results were shown. Overall, the material exhibits more stability and dominance in the faradaic process, which paves the path for improved performance.

Emerging insights into the application of metal-organic framework (MOF)-based materials for electrochemical heavy metal ion detection

Heavy metal ions are one of the main sources of water pollution, which has become a major global problem. Given the growing need for heavy metal ion detection, electrochemical sensor stands out for its high sensitivity and efficiency. Metal-organic frameworks (MOFs) have garnered much interest as electrode modifiers for electrochemical detection of heavy metal ions owing to their significant specific surface area, tailored pore size, and catalytic activity. This review summarizes the progress of MOF-based materials, including pristine MOFs and MOF composites, in the electrochemical detection of various heavy metal ions. The synthetic methods of pristine MOFs, the detection mechanisms of heavy metal ions and the modification strategies of MOFs are introduced. Besides, the diverse applications of MOF-based materials in detecting both single and multiple heavy metal ions are presented. Furthermore, we present the current challenges and prospects for MOF-based materials in electrochemical heavy metal ion detection.

Facile Synthesis of a Layered Bismuth-Based MOF With Superhydrophobic-Oleophilic Property and High Oil-Water Separation Performance.

Metal organic frameworks (MOFs) are a class of potential superhydrophobic-oleophilic materials. The organic ligands in superhydrophobic MOFs usually contain long alkyl chains, fluorine groups or aromatic rings with large π conjugation, the preparation of which suffers from high cost, complex operation and so on. In addition, the topological structure of MOFs plays an important role in the hydrophobicity, which may be ignored previously. Here we report a superhydrophobic-oleophilic MOF (BiPPA2) obtained by a facile and fast method, which not only displays a large water contact angle of up to 163° and a small sliding angle of nearly equal to 0°, but also exhibits high sorption capacity for multiple oils and organic solvents, well reusability and high oil retention. In addition, BiPPA2 is stable in a wide pH range (0.5-11.0). Finally, the single crystal structure of BiPPA2 is resolved to reveal the intrinsic reason for the super-hydrophobicity. This work may inspire the further design of pristine superhydrophobic MOFs based on a simple method, which enriches the family of superhydrophobic MOFs and has great significance for practical applications.

Hierarchically Porous Structured Adsorbents with Ultrahigh Metal-Organic Framework Loading for CO2 Capture.

Metal-organic frameworks (MOFs) have emerged as promising candidates for CO2 adsorption due to their ultrahigh-specific surface area and highly tunable pore-surface properties. However, their large-scale application is hindered by processing issues associated with their microcrystalline powder nature, such as dustiness, pressure drop, and poor mass transfer within packed beds. To address these challenges, shaping/structuring micron-sized polycrystalline MOF powders into millimeter-sized structured forms while preserving porosity and functionality represents an effective yet challenging approach. In this study, a facile and versatile strategy was employed to integrate moisture-stable and scalable microcrystalline MOFs (UiO-66 and ZIF-8) into a poly(acrylonitrile) matrix to fabricate readily processable, millimeter-sized hierarchically porous structured adsorbents with ultrahigh MOF loadings (∼90 wt %) for direct industrial carbon capture applications. These structured composite beads retained the physicochemical properties and separation performance of the pristine MOF crystal particles. Structured UiO-66 and ZIF-8 exhibited high specific surface areas of 1130 m2 g-1 and 1431 m2 g-1, respectively. The structured UiO-66 achieved a CO2 adsorption capacity of 2.0 mmol g-1 at 1 bar and a dynamic CO2/N2 selectivity of 17 for a CO2/N2 gas mixture with a 15/85 volume ratio at 25 °C. Furthermore, the structured adsorbents exhibited excellent cyclability in static and dynamic CO2 adsorption studies, making them promising candidates for practical application.

Anchoring Ni(II) bisacetylacetonate complex into CuS immobilized MOF for enhanced removal of tinidazole and metronidazole

Here in this study, a novel ternary CuS/HKUST‒1/Ni(acac)2 nano photocatalyst (CSHK‒Ni) was developed through a facile modification of HKUST‒1 MOF with Ni(acac)2 metal complex and by immobilizing CuS into the metal-organic framework (MOF). The incorporation of CuS, a narrow bandgap semiconductor, is anticipated to allow easy excitation by visible-light and improve the photocatalytic potential of the formulated catalyst which is validated by the decrease in the bandgap energy from 3.10 eV of pristine MOF to 2.19 eV. Moreover, the anchoring of the metal complex improves the light harvesting behavior by increased conjugation. Photoluminescence studies provided evidence of the effective separation of the photoinduced charge-carriers, reducing the rate of recombination and enhancing the photocatalytic potential of the CSHK‒Ni nanocomposite. The engineered catalyst displayed remarkable efficiency in the degradation of nitroimidazole containing antibiotics, Tinidazole (TNZ) and Metronidazole (MTZ), via H2O2 assisted AOP achieving a maximum photocatalytic efficiency of 95.87 ± 1.64% and 97.95 ± 1.33% in just 30 min under irradiation of visible light at optimum reaction conditions. The possible degradation pathway was elucidated based on the identification of ROS and degradation intermediates via HR‒LCMS and quenching experiments. Meanwhile, the chemical oxygen demand (COD) and total organic carbon (TOC) removal were also examined, encompassing the discussing of various aspects including reaction conditions, influence of various oxidizing agents, competing species and dissolved organic substrates present in the wastewater, marking the novelty of the study. This research elucidated the role of the CSHK‒Ni nanocomposite as an interesting photocatalyst in the elimination of emerging nitroimidazole containing pharmaceutical pollutant under visible-light exposure, presenting an exciting novel avenue for a cleaner and greener environment in the days to come.

A facile strategy for synthesis of flower-like FeNiS2 nanocomposite via integration of binary metal-organic framework and metal sulfide for enhanced electrocatalytic oxygen evolution reaction

Researchers are looking into boosted functional materials to address the rising demand for enhanced energy storage and efficient catalysts in producing and storing sustainable energy. Here, we report the development of an integrated binary metallic FeNi metal-organic framework (MOF) through a unique method termed reductive electrosynthesis. This MOF provides customized catalytic sites inside a highly porous material by connecting metal cations via 2-amino terephthalic acid connectors. However, the poor electrical conductivity and stability of pristine MOFs have made their practical implementation difficult. A thin FeNiS2/nickel foam (NF) nanocomposite based on the precursor and self-sacrificed FeNi-MOF template was developed to get beyond these restrictions. In addition to improving electrical conductivity, this unique structure supports FeNi-MOF porous structure. As a result, the outstanding functional electrocatalytic performance of FeNiS2/NF on oxygen evolution reaction in alkaline media was observed at low overpotential of ηj10 = 280 mV and a tafel slope of 35 mV/dec. This study provides a feasible way to produce highly stable and active nonprecious electrocatalysts for commercial water electrolysis applications.

Enhanced overall water splitting by morphology and electronic structure engineering on pristine ultrathin metal-organic frameworks

Metal-organic frameworks (MOFs) have caused extensive attention attributed to their widespread applications including electrocatalysis by virtue of their distinctive structural characteristics. However, the direct application of pristine MOFs as bifunctional electrocatalysts is quite challenging due to their insufficient active sites and poor electrical conductivity. In this research, the ultrathin tri-metal (Fe, Co, and V) doped FeCoV-NiMOF nanosheet arrays were prepared through a facile hydrothermal method. Benefiting from the distinctive ultrathin (1.5 nm) nanosheet arrays and electronic structure reconfiguration induced by heteroatom doping, the prepared FeCoV-NiMOF displays the low overpotentials of 238, 309, and 408 mV for oxygen evolution reaction (OER) and 144, 255, and 349 mV for hydrogen evolution reaction (HER) at the current densities of 10, 100, and 1000 mA cm−2, respectively, outperforming the vast majority of previously reported bifunctional pristine MOFs. The electrolytic cell utilizing FeCoV-NiMOF as both cathode and anode requires just 1.61 V to attain 10 mA cm−2 and displays superior stability of 100 h at 100 mA cm−2. In the anion exchange membrane electrolyzer, as-prepared FeCoV-NiMOF needs a low cell voltage of 2.16 V at 500 mA cm−2 for effective overall water splitting, demonstrating its substantial potential as bifunctional electrodes for H2 production. The viable and efficient strategy in this study exhibits great prospects to enrich the exploration of bifunctional MOF-based electrocatalysts with superior performance for renewable energy conversion.

Investigating the Structure of Defects in Heterometallic Zeolitic Imidazolate Frameworks ZIF-8(Zn/Cd) and Its Interaction with CO2 Using First-Principle Calculations

Inducing defect in metal-organic frameworks (MOFs) is one of the strategies to modify the structure and properties of this functional material. Defect may occur in a pristine MOF due to missing organic linkers, metal centres and/or other structural behaviours. In this study, the structure of defects in multicomponent MOFs especially heterometallic MOFs of zeolitic imidazolate framework (ZIF-8(Zn/Cd)) was examined to unveil the possible preference defect formation due to missing 2-methylimidazolate (MeIm) and metal centres of Cd2+ and Zn2+. Assuming defect formation due to the reaction between ZIF-8(Zn/Cd) and water, MeIm linker removal is energetically lower than removing metal centres of either Cd2+ or Zn2+. But, the MeIm linker is easier to be removed when it is connected to Cd2+ (Cd-MeIm-Cd) than when it is connected to Zn2+ (Zn-MeIm-Zn). Defect in ZIF-8(Zn/Cd) affects the band gap energy to give slightly lower value than it in pristine ZIF-8(Zn/Cd). Non-covalent interaction (NCI) and interaction region indicator (IRI) analyses were also performed to indicate possible intermolecular forces such as van der Waals and attractive forces present in non-defective and defective ZIF-8(Zn/Cd). The presence of defects in mixed-metal ZIF-8(Zn/Cd) was also tested for its potential use on CO2 adsorption. The interaction energy of CO2 inside defective ZIF-8(Zn/Cd) indicates an exothermic behaviour where CO2 molecule has a preference to be adsorbed inside the framework. This is especially when the capping agents at the defective ZIF-8(Zn/Cd) sites are removed to give open metal sites. This study provides insight how defects in multicomponent MOFs might presence affecting the structural and properties changes. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Metal-Organic Framework-Based Materials for Heavy Metal Sensing in Aqueous Media

Industrial development leads to an increasing amount of pollutants including heavy metal ions in surface and subsurface waters. For instance, wastewater from battery manufacturing, paint manufacturing or metal plating, contain heavy metals in high concentrations. The heavy metals are typically non-biodegradable and not-easy to excrete. Their presence within the organisms causes damage and failure of different organs. Consequently, the permissible concentrations of heavy metal ions in drinking water set by the World Health Organization are on a ppb level.In this work, electrode materials based on metal-organic frameworks (MOFs) are prepared and studied for sensing of heavy metals in aqueous media. These involved MOFs in their pristine form, composites of pristine MOFs and conducting polymer polyaniline as well as their carbonized derivatives. Cadmium and lead ions were used as model pollutants. Thorough physico-chemical characterization of the prepared materials was done using scanning electron microscopy, Raman spectroscopy, and dynamic light scattering. Electroanalytical performance was scrutinized using anodic stripping voltammetry and correlated with materials’ structural, morphology and textural properties. Limits of detection and sensitivity were determined upon optimization of the experimental conditions to identify the best material. Moreover, materials proved to be suitable for two heavy metal ions sensing in real river samples. Acknowledgments This work was supported by the Science Fund of the Republic of Serbia, grant number 7750219, Advanced Conducting Polymer-Based Materials for Electrochemical Energy Conversion and Storage, Sensors and Environmental Protection-AdConPolyMat (IDEAS programme).

Engineering CALF-20/graphene oxide nanocomposites for enhancing CO2/N2 capture performance

Ever-increasing atmospheric CO2 concentrations has necessitated the development of novel and cost-effective nanostructured composites with favorable physicochemical properties. Recently, the potential of metal-organic framework (MOF)-based nanocomposites towards boosting CO2 capture capability has become apparent indicating the importance of the relationship between their structure and properties. Herein, a novel nanocomposite of zinc-based CALF-20 MOF hybridized with graphene oxide is successfully fabricated using the solvothermal method. The construction of the well-structured nanocomposite is confirmed by performing PXRD, BET, FTIR, FESEM/EDX, TEM, and TGA characterization analyses. CO2 and N2 adsorption capacities and CO2/N2 separation performance of these nanocomposites are evaluated by experiment and mathematical modeling for the first time. The CALF-20/GO interfacial interaction and CO2 adsorption mechanisms are also discussed. As the best-performing adsorbent, the CALF-20 containing 20 wt% GO indicates a 42.6 % increment in CO2 uptake at 1.6 bar and a 32.7 % enhancement in CO2/N2 selectivity at 1 bar and 298 K and 1.28 times more CO2 retention time in a fixed bed column compared to that of the pristine MOF. The results show that the MOF and GO form chemical bonds at the interface resulting in generating new pore structures and increasing the porosity which are mostly responsible for boosting CO2 capture capacity. Interestingly, no meaningful effect is observed by the variation of the zinc atomic concentration at the surface. The simple synthesis procedure and understanding the interfacial structure of the novel CALF-20/GO composite as a promising adsorbent for CO2 capture applications can provide new insights for future work.